Unable to add a source with url https://github.com/CocoaPods/Specs.git named master-1.
在pod install或pod update时出现如题的错误提示：
Setting up CocoaPods master repo
[!] Unable to add a source with url https://github.com/CocoaPods/Specs.git named master-1.
You can try adding it manually in ~/.cocoapods/repos or via pod repo add.
错误的原因可能有很多种，其中有可能是升级了Xcode或是安装了新的Xcode，首先要让系统指定一个Xcode
解决办法是：
1、进入/users/用户名/.cocoapods/repos，删除master文件夹
2、重新下载CocoaPods仓库
使用下面的命令
git clone https://git.coding.net/CocoaPods/Specs.git ~/.cocoapods/repos/master
当然你可以用下面方法（备用）
pod repo add master https://github.com/CocoaPods/Specs.git
下载仓库后如有必要pod setup一下
